The published literature contains numerous examples where the problem of reducing the volume requirement of Freon-11, blowing agent, has been addressed.
Replacement of the hard CFC by soft CFC's, such as for example, Freon R-21, R-22 and R-123 is taught by Patents JP No. 52/154,156-A, U.S. Pat. No. 4,636,529 A, and U.S. Pat. No. 4,076,644.
Complete replacement of the Freon-11 blowing agent by non-fluorocarbon blowing agents is taught for example by Japanese Patent No. J 55/094,296 A, whereby a combination of dichloromethane and water are used to blow the foam. Similarly, U.S. Pat. No. 4,264,744 A teaches the use of dichloromethane and selection of catalyst for replacing all or a part of the conventional fluorocarbon blowing agent in the preparation of soft foams.
U.S. Pat. No. 4,417,002 A teaches the use of carboxylic acids in combination with isocyanates to release a gas useful as a blowing agent in the preparation of flexible polyurethane foam.
All modifications taught to address the problem of replacing Freon-11 as blowing agent for polyurethane foams in general follow the pattern of directly substituting the Freon-11 by an alternative blowing agent. For example, foams can be prepared by blowing with water. The water reacts with isocyanate leading to the generation of carbon dioxide which then expands the reacting mixture to give the cellular structure of the polymer.
While water can be used as the only blowing agent, the foams produced do not always exhibit the desired physical properties in comparison to those produced using halocarbon blowing agents, and they are, for example, harder and of poorer resilience.
Mono-alcohols have been used to modify polyisocyanates which are then used in the preparation of polyurethanes. As an example, Japanese Patent JP No. 62/121,719 uses a mono-alcohol to modify a polyisocyanate composition used in the preparation of soft polyurethane foam in situations where heat adhesive properties to fibrous materials are required. Another example is the Patent GB No. 2,188,055 which teaches the preparation of hydrophilic polyurethane foams from 1,6-hexamethylene diisocyanate modified by reaction with a mono-alcohol.
Mono-alcohols have been incorporated into polyol compositions for the purpose of providing low viscosity formulations with good flow characteristics. U.S. Pat. No. 4,715,746 teaches a polyol composition containing mono-alcohols of molecular weight 32 to 600, especially tertiary butanol or isobutanol, to provide permanent strengthening of geological formations in underground workings or mines. Similarly in the French Patent No. 2,312,520 polyglycol monoethers are used as viscosity depressants of polyol compositions required in the preparation of rigid and semi-rigid polyurethane foam. The reduced viscosity of the polyol mixture permits the high pressure continuous casting machines to operate without overheating.
U.S. Pat. No. 3,405,077 teaches the use of mono-alcohols of hydroxyl equivalent weight from 74 to 150 in combination with polyether polyols for the preparation of soft polyurethane foams by reaction with polyisocyanates in the presence of trichlorofluoromethane and water. Similarly Canadian Patent No. 787,977 teaches the use of low molecular weight mono-alcohols for preparing soft polyurethane foam in the presence of mainly trichlorofluoromethane as the blowing agent.
The preparation of flexible slabstock polyurethane foam with polyol compositions containing monohydroxy polyether polyols of equivalent weights up to 719 is taught by Arceneaux, Journal of Elastomers and Plastics, p. 63, Vol. 14 (1982). They note an improvement in elongation properties but observe unacceptable load bearing, tear resistance, and compressive and tensile strength properties of the foams.
It was therefore an object of this invention to define a process which reduces and/or essentially avoids the use of chlorofluorocarbon (CFC) blowing agents for the preparation of soft flexible polyurethane foam and provides products having good physical properties.